Control device for an internal combustion engine

Abstract

The present invention controls ignition timing appropriately while an increment correction of the fuel injection amount is implemented. A control device of the invention determines a retard angle based on a difference between a prior increment factor, which is determined prior to an actual increment of the fuel injection amount in response to loading of the engine and an OTP fuel increment correction factor for determining the actual increment of the fuel injection amount. The engine load may be determined by intake air quality and rotating speed. When the increment correction is delayed for a fixed time period, the structure of the invention effectively prevents the ignition timing from being retarded excessively due to frequent knocking at the beginning of the delay time. This accordingly prevents the ignition timing from being maintained in the retarding condition to undesirably lower the power of the engine when the delay time has elapsed and an actual increment of the fuel injection amount has been executed. In the ignition timing control of the invention, an increase in retard angle immediately affects the ignition timing control while a decrease in retard angle slowly affects the ignition timing control. This allows the ignition timing to be controlled appropriately without undesirable delay.

What is claimed is: 
     
       1. A control device disposed in an internal combustion engine for controlling an air/fuel ratio of said internal combustion engine, said control device comprising: detection means for detecting an operating condition of said internal combustion engine which affects control of said air/fuel ratio of said internal combustion engine;   means for (i) comparing the detected operating condition with a predetermined value that corresponds to a condition that the air/fuel ratio of said internal combustion engine should be made richer, and (ii) determining when the detected operating condition reaches the predetermined level;   air/fuel ratio controlling means for making the air/fuel ratio richer a fixed time period after said means for comparing determines that the detected operating condition has reached the predetermined level;   operating means for determining a parameter representing a difference between a probability of said internal combustion engine knocking before said fixed time period and a probability of said internal combustion engine knocking after said fixed time period; and   ignition timing retarding means for retarding ignition timing during said fixed time period based on said parameter determined by said operation means.   
     
     
       2. A control device in accordance with claim 1, wherein said operation means determines said parameter based on a difference between air/fuel ratios before and after said fixed time period. 
     
     
       3. A control device in accordance with claim 1, wherein said operation means determines said parameter based on a difference between knocking-frequencies before and after said fixed time period. 
     
     
       4. A control device in accordance with claim 1, said control device further comprising: retard angle limiting means for limiting a maximum of a retard angle controlled by said ignition timing retarding means based on said parameter.   
     
     
       5. A control device in accordance with claim 1, wherein said control device further comprises: knocking detection means for detecting knocking generated in said internal combustion engine; and   knocking control means, which functions independent of said ignition timing retarding means, for controlling the ignition timing of said internal combustion engine based on a frequency of the knocking detected by said knocking detection means.   
     
     
       6. A control device in accordance with claim 5, wherein said knocking control means further comprises: first means for controlling ignition timing, based on said parameter determined by said operation means, in a retarding direction at a predetermined first speed at a beginning of said fixed time period; and   second means for controlling ignition timing, based on said parameter determined by said operation means, in an advancing direction at a predetermined second speed, which is slower than said predetermined first speed, at an end of said fixed time period.   
     
     
       7. A method of controlling an air/fuel ratio of an internal combustion engine, said method comprising the steps of: (a) detecting an operating condition of said internal combustion engine which affects control of said air/fuel ratio of said internal combustion engine;   (b) comparing the detected operating condition with a predetermined value that corresponds to a condition that the air/fuel ratio of said internal combustion engine should be made richer, and determining when the detected operating condition reaches the predetermined level;   making the air/fuel ratio richer a fixed time period after it is determined that the detected operating condition has reached the predetermined level;   (c) determining a parameter representing a difference between a probability of knocking before said fixed time period and a probability of knocking after said fixed time period; and   (d) retarding ignition timing of said internal combustion engine during said fixed time period based on said parameter determined in said step (c).   
     
     
       8. A method in accordance with claim 7, wherein said method further comprises the steps of: detecting knocking generated in said internal combustion engine during a time period other than said fixed time period; and   controlling ignition timing of said internal combustion engine based on a frequency of the detected knocking, said step of controlling ignition timing comprising the steps of: (1) retarding the ignition timing, based on said parameter determined in said step (c), at a predetermined first speed at a beginning of said fixed time period; and   (2) advancing the ignition timing, based on said parameter determined in said step (c), at a predetermined second speed, which is slower than said predetermined first speed, at an end of said fixed time period.     
     
     
       9. A control device in accordance with claim 2, wherein said control device further comprises: knocking detection means for detecting knocking generated in said internal combustion engine; and   knocking control means, which functions independent of said ignition timing retarding means, for controlling the ignition timing of said internal combustion engine based on a frequency of the knocking detected by said knocking detection means.   
     
     
       10. A control device in accordance with claim 3, wherein said control device further comprises: knocking detection means for detecting knocking generated in said internal combustion engine; and   knocking control means, which functions independent of said ignition timing retarding means, for controlling the ignition timing of said internal combustion engine based on a frequency of the knocking detected by said knocking detection means.   
     
     
       11. A control device in accordance with claim 4, wherein said control device further comprises: knocking detection means for detecting knocking generated in said internal combustion engine; and   knocking control means, which functions independent of said ignition timing retarding means, for controlling the ignition timing of said internal combustion engine based on a frequency of the knocking detected by said knocking detection means.   
     
     
       12. A control device in accordance with claim 9, wherein said knocking control means further comprises: first means for controlling ignition timing, based on said parameter determined by said operation means, in a retarding direction at a predetermined first speed at a beginning of said fixed time period; and   second means for controlling ignition timing, based on said parameter determined by said operation means, in an advancing direction at a predetermined second speed, which is slower than said predetermined first speed, at an end of said fixed time period.   
     
     
       13. A control device in accordance with claim 10, wherein said knocking control means further comprises: first means for controlling ignition timing, based on said parameter determined by said operation means, in a retarding direction at a predetermined first speed at a beginning of said fixed time period; and   second means for controlling ignition timing, based on said parameter determined by said operation means, in an advancing direction at a predetermined second speed, which is slower than said predetermined first speed, at an end of said fixed time period.   
     
     
       14. A control device in accordance with claim 11, wherein said knocking control means further comprises: first means for controlling ignition timing, based on said parameter determined by said operation means, in a retarding direction at a predetermined first speed at a beginning of said fixed time period; and   second means for controlling ignition timing, based on said parameter determined by said operation means, in an advancing direction at a predetermined second speed, which is slower than said predetermined first speed, at an end of said fixed time period.   
     
     
       15. A control system disposed in an internal combustion engine for controlling an air/fuel ratio of said internal combustion engine, said control system comprising: a sensor which detects an operating condition of said internal combustion engine which affects control of said air/fuel ratio of said internal combustion engine;   an electronic control unit, receiving the detected operating condition, functioning to: (1) compare the detected operating condition with a predetermined value that corresponds to a condition that the air/fuel ratio of said internal combustion engine should be made richer, and determine when the detected operating condition reaches the predetermined level,   (2) control a fuel injector to make the air/fuel ratio richer a fixed time period after it is determined that the detected operating condition has reached the predetermined level,   (3) determine a parameter representing a difference between a probability of said internal combustion engine knocking before said fixed time period and a probability of said internal combustion engine knocking after said fixed time period, and   (4) retard ignition timing during said fixed time period based on said parameter.